1. Field of the Invention
The present invention relates to a glass antenna for a windshield of an automotive vehicle, particularly, for a side windshield (also called, a side window glass) of the vehicle, the glass antenna being especially suitable for receiving electromagnetic waves of both FM (Frequency Modulation) broadcasting waves and AM (Amplitude Modulation) broadcasting waves.
2. Description of the Related Art
Examples of glass antennas for automotive vehicles having heretofore known and put into practice are an antenna attached to a marginal area or space of a rear window glass (a rear windshield) above or below a defogger electric heating element and an antenna including a conductive strip provided to a front window glass (a front windshield).
The former antenna, however, is not always capable of attaining a sufficient reception gain since the space occupied by the antenna is required to be small for eliminating a possibility that the antenna makes poor a visibility (a field of view).
The latter antenna, namely, the antenna provided to the front windshield can attain a relatively high reception gain but is encountered by a larger restriction on its attaining place than the rear windshield so that it never blocks driver""s visibility (driver""s field of view).
Various types of glass antennas attached onto the side window glass (hereinafter, referred to the side windshield) have been proposed since no such a restriction as described above has been placed on the side windshield and a recreational vehicle (RV car) has come to be widely used on which each side windshield, each side windshield having a relatively wide area, is attached.
A Japanese Patent Application First Publication No. Heisei 10-93317 published on Apr. 10, 1998 exemplifies a first previously proposed AM-and-FM frequency band receivable glass antenna for the side windshield.
In the first previously proposed glass antenna, a first antenna element is arranged along a proximity to a whole window frame edge, a feed terminal for the antenna elements is arranged on a proximity to one corner of the side windshield, and five or more horizontally extended antenna elements are arranged at an equal spatial interval of 5 millimeters or longer.
A Japanese Patent Application First Publication No. Heisei 10-303625 published on Nov. 13, 1998 exemplifies a second previously proposed AM broadcasting, FM broadcasting, and television broadcasting wave receivable glass antenna.
The second previously proposed glass antenna includes a first antenna conductor, a second antenna conductor, a third antenna conductor, a first feed terminal, and a second feed terminal. The first antenna conductor connected to the second feed terminal includes a plurality of antenna elements extended approximately in parallel to one another, one end of each of the antenna elements being connected to a corresponding one end of the others of the antenna elements. The second antenna conductor is extended from the first feed terminal, is of a semi-circular antenna element enclosing a surrounding of the first antenna conductor, and is electrically connected to at least one of the plurality of antenna elements of the first conductor.
In addition, a Japanese Patent Application First Publication No. Heisei 10-65430 published on Mar. 16, 1998 exemplifies a third previously proposed vehicular glass antenna.
In the third previously proposed vehicular glass antenna, a feed terminal and a loop-shaped or semi-loop shaped main antenna conductor connected to the feed terminal are attached onto a vehicular window glass plate. A sub-antenna conductor is added to at least one of either upper or lower loop-shaped main antenna conductor, is extended in an approximately longitudinal direction of the glass plate, and is extended approximately in parallel to the main antenna conductor.
Furthermore, a Japanese Patent Application First Publication No. Heisei 10-13127 published on Jan. 16, 1998 exemplifies a fourth previously proposed vehicular glass antenna suitable for receiving AM radio broadcasting waves and FM radio broadcasting waves.
The fourth previously proposed vehicular glass antenna includes: a first horizontal wire segment extended from a feed terminal disposed on one corner of the vehicular side windshield plate along a lower side edge or an upper side edge; a first vertical wire segment extended from a tip of the first horizontal wire segment toward an approximately center of one side edge; a second horizontal wire segment extended horizontally from a tip of the first vertical wire segment toward an approximately center of the other side edge; a second vertical wire segment extended from a tip of the second horizontal wire segment to either an upper side or lower side which is opposite to the first horizontal wire segment; and a third horizontal wire segment extended from a tip of the second vertical wire segment along either the upper or lower side edge which is opposite to the first horizontal wire segment.
There are many RV cars whose rear windshield plate can be opened or closed. Since such a coaxial cable wired from the antenna attached to the rear windshield plate of each RV car described above is repeated to be bent due to a repetitive open or closure of the rear windshield plate, the repetitive bending of the coaxial cable tends to provide a cause of a failure such as a wire breakage or imperfect contact in the glass antenna.
In addition, since, even in the case of the RV cars whose rear windshield plates cannot be opened nor closed, a dimension of the rear windshield plate of each RV car described above is rather small and an assembly angle of the antenna to the windshield is almost near to a right angle and the occupied area of the glass antenna at the marginal area upper or lower than the defogging heating wire segments becomes narrow.
If the antenna elements are attached onto such a marginal area or space as described above, the glass antenna cannot obtain a sufficient reception gain. This is remarkable in a case of the antenna elements by which the AM radio broadcasting waves having low reception frequencies and FM radio broadcasting waves are received.
Recently, a radio broadcasting wave receiving antenna attached onto the side windshield of the vehicle has been demanded.
A directivity of the glass antenna attached onto one side windshield located at a driver""s seat side or at the same directional rearward side of the vehicle is different in a reception gain from that located at a passenger""s seat side or at the same directional rearward side of the vehicle. There is a antenna arranged direction in which the directivity is low. That is to say, in a case where the glass antenna is attached onto the side windshield located at the driver""s seat side, a favorable reception state can be obtained for the electromagnetic waves arriving at the vehicle from an upper sky viewed from the driver""s seat side. However, a sufficient reception gain is difficult to be obtained for the electromagnetic waves arriving at the passenger""s seat side.
In addition, each of the first, second, and third previously proposed vehicular glass antennas disclosed in the above-described Japanese Patent Application First Publications No. Heisei 10-93317, Heisei 10-303625, and Heisei 10-65430 is attached onto the side windshield and has a relatively small area. Although a reception sensitivity on the AM radio broadcasting waves is favorable, the reception sensitivity of the FM radio broadcasting waves is not sufficient.
Furthermore, the fourth previously proposed vehicular glass antenna for the side windshield disclosed in the Japanese Patent Application First Publication No.
Heisei 10-13127 is used mainly for the reception of the FM radio broadcasting waves, Although it is possible to receive the AM radio broadcasting waves, the reception sensitivity is rather insufficient. The area of the glass plate cannot help being widened.
It is therefore an object of the present invention to provide a non-directivity glass antenna for a side windshield of an automotive in which antenna elements which are capable of receiving AM radio broadcasting waves with a high reception sensitivity in addition to being capable of receiving FM radio receiving broadcasting waves with a superior directivity characteristic are effectively disposed on the side windshield.
The above-described object can be achieved by providing a glass antenna for a windshield for an automotive vehicle, comprising: a feed terminal disposed on a proximity to a first corner of the windshield; a substantially letter-S shaped antenna element comprising: a first wire segment extended from the feed terminal at the proximity to the first corner toward a substantially opposite direction to the first corner along at least a first side edge of the windshield; a second wire segment extended from a tip of the first wire segment toward a proximity to a center of a second side edge of the windshield; a third wire segment extended from a tip of the second wire segment toward a proximity to a second corner of the windshield which is opposite to the first corner; and a fourth wire segment extended from a tip of the third wire segment toward a substantially opposite direction to the second corner along a third edge of the windshield; and a plurality of other antenna elements, the other antenna elements being connected to the feed terminal and extended in parallel to one another in a first space defined between the first and second wire segments and in a second space defined between the second, third, and fourth wire segments.
The above-described object can also be achieved by providing a glass antenna for a side windshield of an automotive vehicle, the side windshield comprising a general shape of a parallelogram and the glass antenna comprising: a feed terminal disposed on a proximity to a first corner of the side windshield; a substantially letter-S shaped antenna element comprising: a first horizontal wire segment extended from the feed terminal toward a horizontally opposite direction to the first corner along a first side edge of the side windshield; a first vertical wire segment extended from a tip of the first horizontal wire segment toward a proximity to a center of a second side edge of the side windshield; a second horizontal wire segment extended horizontally from a tip of the first vertical wire segment toward a proximity to a center of a third side edge of the side windshield which is opposite to the proximity to the center of the first side edge thereof; a second vertical wire segment extended vertically from a tip of the second horizontal wire segment toward a proximity to a second corner of the side windshield; and a third horizontal wire segment extended from a tip of the second vertical wire segment toward a proximity to a third corner of the side windshield; and a plurality of other antenna horizontal elements connected to the feed terminal and extended in parallel to one another in a first space defined between the first horizontal and first vertical wire segments and the second horizontal wire segment and in a second space defined between the second horizontal, the second vertical, and the third horizontal wire segments.
The above-described object can also be achieved by providing a glass antenna for a side windshield of an automotive vehicle, the side windshield comprising a general shape of a right triangle and the glass antenna comprising: a feed terminal disposed on a proximity to a first corner of the side windshield; a substantially letter-S shaped antenna element comprising: a first arc-shaped wire segment extended from the feed terminal toward a substantially horizontally opposite direction to the first corner along a side edge faced toward a body flange and toward a proximity to a center of the side edge; a second horizontal wire segment extended horizontally from a tip of the arc-shaped wire segment toward a proximity to a center of another side edge of the side windshield which is opposite to the proximity to the body flange; and a second vertical wire segment extended vertically from a tip of the second horizontal wire segment toward a proximity to a second corner of the side windshield; and a third horizontal wire segment extended from a tip of the second vertical wire segment toward a substantially opposite direction to the second corner of the side windshield; and a plurality of other antenna horizontal elements connected to the feed terminal and extended in parallel to one another in a first space defined between the first arc-shaped and second horizontal wire segments and in a second space defined between the second horizontal wire segment, the second vertical wire segment, and the third horizontal wire segment.